1. Field of the Invention
The present invention relates to rotary machines and, more particularly, to rotary machines of the type having vanes which slide relative to a rotor.
2. Prior Art
Rotary vane machines typically include a stator housing having an inner surface defining a stator chamber and inlet and outlet ports, a rotor, and a plurality of vanes. The rotor is rotatably mounted within the stator chamber and supports the vanes for rotation while permitting them to slide relative to the rotor in order to maintain contact between the tips of the vanes and the inner surface of the stator housing. In machines of this type, the rotor typically is mounted for rotation about an axis which is off-center or eccentric with respect to the stator chamber so that the outer surface of the rotor, the surfaces of the vanes, and the inner surface of the stator chamber define discrete chambers which vary volumetrically as the rotor rotates within the stator housing.
Many mechanisms have been employed to position the vanes properly with respect to the rotor so that the vanes will slide in a radial direction with respect to the rotor to maintain contact with the inner surface of the stator chamber and form the desired discrete chambers within the stator housing. For example, U.S. Pat. No. 2,314,056 discloses a rotary vane vacuum pump or compressor having a cylindrical stator housing within which is mounted a hollow inner body having a cylindrical internal surface. A hollow, cylindrical driving member is rotatably mounted within the inner body and defines pairs of opposing slits which slidably receive vanes. The vanes are connected to each other such that rotation of the cylindrical driving member causes the vanes to rotate and to slide with respect to the driving member. The driving member is mounted within the hollow inner body so that it is off-center from a central axis of the inner body.
The vanes extend from and retract into the cylindrical driving member so that they form discrete chambers within the hollow inner body which are defined by the vane surfaces, the outer surface of the driving member, and the inner surface of the inner body. The vanes comprise a first vane member which is H-shaped and a second vane member which is substantially rectangular with a rectangular opening formed in its center. The two vane members are connected by a crank arrangement consisting of journals and connecting rods. A disadvantage of this device lies in the fact that it is designed only to accommodate two sets of opposing vanes and does not lend itself to applications requiring more than two sets of vanes.
U.S. Pat. No. 2,781,729 discloses a fluid pump comprising a housing which is circular in cross section and a rotor which is rotatably mounted within the housing. The rotor includes slots which slidably receive sets of vanes which in turn are rotatably mounted to sleeves. The sleeves are carried on bearings which rotate about eccentric bearing bosses. The bearing bosses are rotated by a shaft whose end is disposed within the housing.
The pairs of vanes are rigidly connected to each other by the sleeves and are disposed within the housing such that the pairs of vanes are spaced about a central axis of a drive shaft. During operation of the pump, the vanes oscillate or swing relative to the sleeves which carry them. This oscillating movement is undesirable in that it accelerates wear between the parts and shortens the operating life of the pump.
Another example is shown in U.S. Pat. Nos. 1,940,384 and 1,637,484. Each patent discloses a rotary machine having a rotor mounted eccentrically within a substantially cylindrical chamber and which defines slots which slidably receive vanes which are carried on a central shaft, also mounted eccentrically within the chamber. In the device disclosed in the former patent, the vanes are joined to form pairs by members which define oblong slots extending along a centerline of the vane pairs. During operation of this machine, the central shaft oscillates within the oblong slots of the joining members.
In one embodiment of the latter patent, the vanes are also grouped in opposing pairs and are joined by members which define oblong slots. However, these oblong slots are oriented perpendicularly to the slots of the former patent. During operation of this machine, the drive shaft oscillates within the slots.
The two rotary machines disclosed in these patents each have members which join vanes together in pairs and define slots within which the central drive shaft oscillates. This oscillating movement during operation creates excessive wear between the two parts, thereby shortening the useful life of the machine.
Accordingly, there is a need for a rotary vane machine with few working parts to reduce the cost of fabrication, but which can also accommodate more than two sets of vanes. There is also a need for a rotary vane machine having pairs of vanes joined by connecting members and driven by engagement with a central drive shaft which reduces or eliminates oscillating movement between the central drive shaft and the connecting members to reduce wear and extend the useful life of the apparatus.